The present invention relates to microfluidic devices, and more particularly, to a method and apparatus for distributing fluid within or from a microfluidic device.
Methods of making a homologous series of compounds, or the testing of new potential drug compounds comprising a series of light compounds, has been a slow process because each member of a series or each potential drug must be made individually and tested individually. For example, a plurality of potential drug compounds that differ perhaps only by a single amino acid or nucleotide base, or a different sequence of amino acids or nucleotides are tested by an agent to determine their potential for being suitable drug candidates.
The processes described above have been improved by microfluidic chips which are able to separate materials in microchannels and move them through the microchannels. Moving the materials through microchannels is possible by use of various electro-kinetic processes such as electrophoresis or electro-osmosis. Fluids may be propelled through various small channels by the electro-osmotic forces. An electro-osmotic force is built up in the channel via surface charge buildup by means of an external voltage that can repel fluid and cause flow.
Other methods for moving materials through microchannels include, for example, pressure pumping. For this process, pressure heads are attached to the microfluidic chips and small bursts of pressured air or other gas, such as an inert gas; is directed into the microchannels.
Ultimately, the small volumes of liquids formed in the wells or reservoirs of a microfluidic device must be sampled and tested. Previous known methods for distributing and transporting fluids from the microfluidic devices include pressurizing the fluid to allow the fluid or a portion thereof to exit its chamber. One drawback to pressure pumping is that several parameters must be precisely controlled to expel a desired liquid amount. Such parameters include duration, the pulse magnitude, the channel dimension and solution viscosity.
It is, therefore, one object of the invention to provide an improved fluid dispensing system to dispense fluid from reaction wells. It is a further object of the invention to provide a controllable spray or stream of fluid for analysis.
It is yet another object of the present invention to provide a liquid handling drug discovery and diagnostic tool which increases the speed and productivity of discovering new drug candidates and does so on a miniaturized scale or platform that reduces cost and manual handling. It is still a further object of the present invention to provide a multiple fluid sample processor, system and method which is capable of conveying, transporting, and/or processing samples in a large multiplicity of sites.
In one aspect of the invention, a microfluidic fluid transportation system is coupled to a fluid pressure source. A microfluidic device has a fluid input coupled to the fluid pressure source, and a channel having an opening therein. The fluid pressure source pumps fluid into the channel to form a droplet at the opening having a predetermined volume. An electrical contact is proximate the opening and a power source is coupled to the contact. The power source selectively applies electrical power to the contact upon the formation of the droplet of a predetermined volume to form a fluid delivery.
In a further aspect of the invention, an inventive method is utilized which comprises forming a droplet having a predetermined volume of fluid at an outlet, generating a potential difference between the fluid and a target, releasing the fluid, and, directing the fluid at the target.
One advantage of the invention is that small and controlled amounts of fluid may be delivered or transported without the need to control many parameters. Another advantage of the invention is that the method for delivering fluid to microfluidic structures is applicable to structures having high integration densities and where viscous losses in micro channels are significant.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.